Buick/GM Smart Guys

07 Buick Rendezvous 3.5. Replaced battery & alternator 2 months ago. Wife got in it and nothing. No lights, sounds etc. I suspected bad reman alternator killed the battery. It was late so I picked her up. I tried to start it and nothing. Went back in the morning to leave the keys for tow truck. Tried it again and same results. Towed home. While watching on security cameras. Tow driver got in it to roll off roll back. Saw the brake lights come on and reverse lights went he was going to neutral. Rolled it off the truck. Wife went out couple hours later and it started right up. Been fine a couple days now. Suspecting a possible ignition switch(not the key tumblers)
Thoughts???

Maybe it wasn't fully locked in park. If it does it again either try to reseat the shifter into park, or put it in neutral and try to start it. Could be a neutral safety switch.

Maybe it wasn't fully locked in park. If it does it again either try to reseat the shifter into park, or put it in neutral and try to start it. Could be a neutral safety switch.
No that's not it. No dash lights, no door chime, keyless remote does nothing, no interior lights. Completely dark.

Ah, yeah, ignition switch would be my guess too.

Uh-Errh- Brake lights are NOT on ignition switch circuit. I'd say internal open in battery, or bad battery connection/cable. Or bad ground at block/body.

Uh-Errh- Brake lights are NOT on ignition switch circuit. I'd say internal open in battery, or bad battery connection/cable. Or bad ground at block/body.
Valid point. Guess I'll be chasing cabling.

I was able to check it today. Turned the key and no lights or anything. Went under the hood wiggling cables, etc.(nothing noticeable lose) Power restored. Was able to tighten the side battery terminals a little. Checked the grounds and those are clean & tight. So we'll see if the little tightening was the issue.
Thanks.

I'm guessing from here an internal battery open...swap batteries with one of your other cars for a day or two...see what happens to either....does the problem follow the battery?

I'm guessing from here an internal battery open...swap batteries with one of your other cars for a day or two...see what happens to either....does the problem follow the battery?

I do understand battery issues. Since this only is 2 months old, I don't think so. It could be but doubtful.

I've seen brand new batteries short out and have open circuits right off the shelf---so testing is your best way to solve your issue. Just because it's new doesn't mean a thing in this day and age.

I've seen brand new batteries short out and have open circuits right off the shelf---so testing is your best way to solve your issue. Just because it's new doesn't mean a thing in this day and age.
Understand. If it does it again I'll pull it and get it tested. My other vehicles have regular top posts.

If it is truly an intermittent open circuit inside the battery, it will probably test fine. Last time this happened to me, I walked it in, threw it on their counter and demanded another new battery. They understood the failure mode and replaced it. But it was already a warranty replacement, and they said they could only give me a new battery, with no warranty now! This is Autozone. I had no choice but to walk out with the new battery...but the good news is, it fixed my intermittent no start issues. They did not even test it- just gave me the battery, did not put anything in the computer. I had that battery for about two months before I even put it in my vehicle-- they judged it by the date sticker on the batter.

So far no repeat of the symptoms.

I am so glad that when I logged on one of the first threads I saw was on Buick and GMs. To be completely honest, I have never been a big Buick guy or know much about them, but I did just purchase an '85 Skyhawk (I know, I know, the sportiest car out there) and I just want to make it simply fun to drive. Any tips that pertain to just GMs?